<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            min-width: 600px;
        }

        .center {
            /* css3 计算函数  运算符记得加空格 */
            width: calc(100% - 300px);
            height: 150px;
            background-color: #94E8FF;
            float: left;
        }

        .left {
            width: 100px;
            height: 150px;
            background-color: #FFB5BF;
            float: left;
        }

        .right {
            width: 200px;
            height: 150px;
            background-color: #8990D5;
            float: left;
        }
        .navbar{
            border: 1px solid red
        }
        .navbar::after{
            content: '';
            display: block;
            visibility :hidden;
            clear: both;
            height: 0;
        }
    </style>
</head>

<body>
    <div class="navbar">
        <div class="left">left</div>
        <div class="center">center</div>
        <div class="right">right</div>
    </div>
</body>

</html>